如何在 java 13 或更高版本中格式化 OffsetDateTime？

Question

In Java 11, clock system uses millisecond precision, but apparently in Java 13 and above, it uses microsecond precision and this causes my tests to fail. As an example, OffsetDateTime.now() gives me this date "2021-12-10T10:58:05.309594500+01:00" while when I read this date from database "2021-12-10T10:58:05.309595+01:00". I am searching for a way that I can format the first date that I can drop two 00 at the end. I do want having it in OffsetDateTime type not string.

Could you please help me?

Answer 1

An OffsetDateTime always has got nanosecond precision. It's now method may not have depending on platform and Java version. Internally the object has. So there is no way that you can have an OffsetDateTime with fewer than 9 decimals on the seconds.

How many decimals are printed is a different question. What is really printed when you print an OffsetDateTime is a String . If you just print the object, its toString method is implicitly called to produce the string that we see in print. OffsetDateTime.toString() always gives us as many groups of 3 decimals as are necessary for rendering the full precision. So if the decimals were .100000000 , then .100 is printed. If they were .309594500 , as you have seen already, all 9 decimals are present in the string. There is no way that you can change this behaviour.

If you want a different string printed, you can use a DateTimeFormatter with the number of decimals you like.

So what you can do:

1. You can modify the OffsetDateTime , or really, you can create a new one like the old one only with more decimals being zero, which in turn may cause fewer decimals to be printed by toString() .
2. You can format the OffsetDateTime into a string of your liking.

The following code snippets combines both options. For formatting only the decimals up to the last non-zero decimal I am using the following formatter:

private static final DateTimeFormatter ODT_FORMATTER = new DateTimeFormatterBuilder()
        .appendPattern("uuuu-MM-dd'T'HH:mm.ss")
        .appendFraction(ChronoField.NANO_OF_SECOND, 0, 9, true)
        .appendOffsetId()
        .toFormatter(Locale.ROOT);

Demonstration:

    OffsetDateTime dateTime = OffsetDateTime.parse("2021-12-10T10:58:05.309594500+01:00");

    int nanos = dateTime.getNano();
    OffsetDateTime with7Decimals = dateTime.withNano(nanos / 100 * 100);
    System.out.println("toString(): " + with7Decimals);
    System.out.println("Formatted:  " + with7Decimals.format(ODT_FORMATTER));
    OffsetDateTime with5Decimals = dateTime.withNano(nanos / 10000 * 10000);
    System.out.println("toString(): " + with5Decimals);
    System.out.println("Formatted:  " + with5Decimals.format(ODT_FORMATTER));

Output:

 toString(): 2021-12-10T10:58:05.309594500+01:00 Formatted: 2021-12-10T10:58.05.3095945+01:00 toString(): 2021-12-10T10:58:05.309590+01:00 Formatted: 2021-12-10T10:58.05.30959+01:00

For you tests I see no reason to use strings for comparison. Just compare the OffsetDateTime objects after setting those decimals to zero that will be lost in your database anyway.